1. Field of the Invention
The present invention relates to a sheet feeder and an image forming apparatus, and specifically to a sheet feeder into which a sheet cassette is loaded in a detachable manner, and an image forming apparatus including the sheet feeder.
2. Description of the Related Art
Conventionally, for an image forming apparatus such as a printer, a facsimile, and a copier, there has been known one including a sheet feeder in which a sheet cassette is detachably loaded into the apparatus body. In the image formation, the sheet feeder feeds a sheet, stored in the sheet cassette, to an image forming portion by a feed roller.
The sheet cassette is provided with a cassette body storing sheets therein and an intermediate plate which is provided in the cassette body so as to rotate in up and down directions around a rotation fulcrum portion and rotates upward to press the sheet, stored in the cassette body, against the feed roller. The sheet cassette is further provided with a rear end regulating member and a side end regulating member. The rear end regulating member is movably provided in the cassette body in a sheet feeding direction and regulates a rear end position of the sheet stored in the cassette body. The side end regulating member is movably provided in a direction (hereinafter referred to as a width direction) perpendicular to the sheet feeding direction and regulates a side end position of the sheet stored in the cassette body.
For example, when the sheet cassette is transported, or when an image forming apparatus is transported in a state of including the sheet cassette detachably loaded therein, the rotation fulcrum portion of the intermediate plate is detached from the cassette body due to vibrations in the transportation, leading to the breakage of the intermediate plate and the feeding failure. Therefore, conventionally, the intermediate plate is prevented from being detached from the cassette body by virtue of the use of a buffer such as foamed polystyrene and cardboard. However, such a buffer is used only in the transportation of the image forming apparatus, and thus after the image forming apparatus is unpacked, the buffer is discarded. Therefore, in view of environment, the use of buffers has been regarded as a problem.
Thus, for a sheet cassette which can prevent the breakage of the intermediate plate without using the above buffers, Japanese Patent Laid-Open Publication No. 2007-031064 discloses a sheet cassette in which in the transportation, the intermediate plate is fixed by, for example, the rear end regulating member or the side end regulating member provided in the cassette body. The rear end regulating member or the side end regulating member is engaged with the intermediate plate to thereby regulate the rotation of the intermediate plate, whereby the detachment of the intermediate plate from the cassette body and the breakage of the intermediate plate can be prevented.
However, after the sheet cassette having the above constitution is transported, a user should move the rear end regulating member, engaged with the intermediate plate, to a position allowing the intermediate plate to freely rotate, which takes a lot of trouble.
If the rotation of the intermediate plate is prevented by, for example, the side end regulating member, the side end regulating member may be contained in the cassette body without moving the side end regulating member at the position where the side end regulating member is engaged with the intermediate plate to prevent the rotation of the intermediate plate. However, in this case, a user may neglect the movement of the side end regulating member, whereby a sheet cannot be fed from the cassette body.
The present invention has been made in view of the above problems, and an object of the invention is to provide a sheet feeder and an image forming apparatus which can reliably feed a sheet without requiring the extra operation of a regulating member.